All babies grow and learn differently, but many four month old babies have developed similar skills, like being able to hold a toy. Babies of this age are also not ready to do some things like crawling. This means some toys are not suitable for a four month old.
It is important for toys to match the age of a baby. This is not only for safety reasons. When the type of toy and the age of a baby is well matched it means the toy will help a baby learn more and will be more fun for them to play with.
These toys all match the typical developmental stage of four month old babies and will be suitable until they are about six months. Some babies even grow to love a toy so much that they play with it far beyond the expected time. This is because playing with a favorite toy can give them a sense of security.
Pictured: Musical Inchworm